Achromatic spectacle-glass.



M. VON ROHR.

AGHROMATIG SPEOTACLE GLASS. APPLICATION FILED JULY 15, 1909.

968,693, I Patented Aug. 30, 1910.

marten stares rnn r carton MQRITZ VON ROI-IR, 0F JENA, GERMANY, ASSIGNOR TO THE FIRM 01E CARL ZEISS, 0F

JENA, GEBMAHY.

ACHBOMATIC SPECTACLE-GLASS.

Specification of Letters Patent.

Patented Aug. 30, idid.

Applicatlon'filed July 15, 1909. Serial No. ?,769.

lective spectacle glasses required for aphacic eyes" and particularly to those which are, for the purpose of chromatic correction, cemented or fused together of a front biconvex crown glass lens and a hinder planoconcave flint glass lens, of which latter the hinder plane surface may be replaced by a cylindrical surface for correcting an astigmatic defect of the eye.' Achromatic spectacle glasses of this description, as are hitherto known, show coarse astigmatic aberrations,

when their marginal parts are made use of.

These aberrations are capable of being removed, although the hinder surface must be a plane one and the curvature of the front surface is nearly fixed by the required power of the spectacle glass. The investigations upon which the. invention is based have proved, that'the great variety of the available kinds of crown and flint glass allows of-realizing such astigmatic correction, without neglecting the chromatic one, for the whole region between 10 and 18 dioptries, to

-which the powers of spectacles for aphacic eyes in the main are restricted. For both corrections there is, as is well known, a small hinder diaphragnrto be supposed in the center of rotation of he eye, 6., about 3 cm. distant from thes cctacle glass.

' in the accompanying -:awing: Figure 1 is an axial section through an anastigmatic and achromatic spectacle glass constructed according to the invention to correct an aphacic eye for distance. Fig. 2 is'an axial section through an anastigmatic and achromatic spectacle glass constructed according to the invention to correct an aphacio eye for reading.

In both spectacle glasses shown in these. figures any astigmatic defect oi the eye 1S left out of consideration. Forithis reason either glass is shown as equipped wlth a plane hinder surface in lieu of a cylindrical one. For each example a table is given below, which contains, besides-the statements as to the power of the spectacle glass and the kinds of glass used forit, thenumerical values of the linear dimensions indicated in the figures, alsothe angles of inclination to and "la of the red and blue components, which on the object side correspond to the principal ray on the image side selected for achromatization, or instead of these angles, the distances h and by between the axis and the places, in which these components impinge on the object plane, then the angles of inclination to of the three principal rays on the object side and the intersection distances a, and s", of the sagittal and meridional pencils appertaining tothe same principal rays on the image side, i. e., the distances between the, exit places of the pencils and their places of intersection.

Fig. 1. Focal length 91.02 mm. Power 11 dloptrics. bbjecm [at distant.

n =1.s1c33 1/ =64.1 o =1.e0291 v =sa1 DI r,=40.92 min. I r,,:50.0 mm. r,=oo H a =mo a =Lo l=25.o mm in -219 .353 iu =19352 w =0 13.481 1934? s :85.09 mm. 87.84 mm. 92.10 mm. 3%,:84109 86.13 94.45

Fig. 2.

Focal length 69.0hnm. Power 14.5 dioptries. Plane object at right angles to the axis and ata distance of 315 mm. from the lens.

11 :1.516S7. :641 n =L59633 v ziiflifi 4 :31.93 mm. r :43.2l mm. 1 :00

(1 :31.0 mm. (1 20.5 mm. 1:250 mm.

11::O ]f.370 16 .343 s,,:82.95 mm. 84.81 mm. 88.34 mm. s,=82.95 82.57 92.06

'1 claim An achromatic collective spectacle glass for an aphacic eye, consisting of two lenses closely joined together, a biconvex collective lens and a dispersive lens, the free surface of the dispersive lens having at least in one direction the curvature zero and thev spectacle glass being corrected for astigmatism with regard to a small diaphragm. placed at about 3 cm. distance from the free surface of the dispersive lens.

MORITZ VON ROI-IR.

Witnesses PAUL Knt'rcnn, FRITZ LANDER. 

